The Power of Movement in Plants

Alopecurus pratensis.—A young plant, 11 inches in height, with the flower-head protruded, but with the florets not yet expanded, had a glass filament fixed close above the second joint, at a height of only 2 inches above the ground. The basal internode, 2 inches in length, was cemented to a stick to prevent any possibility of its circumnutating. The extremity of the filament, which projected about 50° above the horizon, was often observed during 24 h. in the same manner as in the last case. Whenever looked at, it was always in movement, and it crossed 30 divisions of the micrometer (3; inch) in 33 h.; but it sometimes moved ata quicker rate, for at one time it crossed 5 divisions in 1} h. The pot had to be moved occasionally, as the end of the filament travelled beyond the field of vision; but as far as we could judge it followed during the daytime a semicircular course ; and it certainly travelled in two different directions at right angles to one another. It sometimes oscillated in the same manner as in the last species, some of the jerks forwards being as much aS yg55 of an inch. We may therefore conclude that the joints in this and the last species of grass long continue to circumnutate; so that this movement would be ready to be converted into an apogeotropic movement, whenever the stem was placed in an inclined or horizontal position.

Movements of the Flower-peduncles of Oxalis carnosa, due to apogeotropism and other forces—The movements of the main peduncle, and of the three or four sub-peduncles which each mair peduncle of this plant bears, are extremely complex, and are determined by several distinct causes. Whilst the flowers ave expanded, both kinds of peduncles circumnutate about the sare spot, as we have seen (Fig 91) in the fourth chapter. But soon after the flowers have begun to wither the sub-

peduncles bend downwards. and this is due to epinasty; for on two occasions when pots were laid horizontally, the sul peduncles assumed the same position relatively to the main pedunele, as would have been the case if they had remained upright; that is. each of them formed with it an angle of about 40°. If they had been acted on by geotropism or aphelio- tropism (for the plant was illuminated from above). they weuld have directed themselves to the centre of the earth. A main pedunele was secured to a stick in an upright position, and one of the upright sub-peduneles which had been observed cireum- nutating whilst the flower was expanded, continued to do so for at least 24 h. after it had withered. It then began to bend downwards, and after 86 h, pointed a little beneath the horizon. A new figure was now begun, A. Fig. 188), and the sub-pedunele was traced descending ina zigzag line from7.20 P.w. on the 19th to 9 ax. on the 22nd. It now pointed almost perpendicularly downwards, and the glass filament had to be removed and fastened transversely across the base of the young capsule. We expected that the sub-peduncle would have been motionless in its new position; but it continued slowly to swing, like a pendulum, from side to side, that is. in a plane at right angles to that in which it had descended. This cireumnutating move- ment was observed from 9 a.w. on 22nd to 9 a.m. 24th, as shown at B in the diagram. We were not able to observe this par- ticular sub-pedunele any longer: but it would certainly have gone on circumnutating until the capsule was nearly ripe (which requires only a short time), and it would then have moved upwards.

The upward movement (0, Fig. 188) is effected in part by the whole sub-peduncle rising in the same manner as it had pre- viously descended through epinasty—namely, at the joint where united to the main peduncle. As this upward movement occurred with plants kept in the dark and in whatever position the main peduncle was fastened, it could not have been caused by heliotropism or apogeotropism, but by hyponasty. Pesides this movement at the joint, there is another 0. a very different kind, for the sub-peduncle becomes upwardly bent in the middle part. If the sub-peduncle happens at the time to be inelined much downwards, the upward curvature is so great that the whole forms a hook. The upper end bearing the capsule, thus always places itself upright, and as this -ccurs in darkness, and in whatever position the main peduncle may have been secured,

the upward curvadire eannot bo duo to heliotropisms or hypo- uanty, but Co apoyootropisna, Dewy eomasa s movements of dower-pedinelo, traced on a vertical pias AL aMinastie downward movement; By ciyeumnutation whilst de; end: Wa vertically 3 Cy subsequent upward movement, due fo apogeof reps and Vv ponasty combed 1n order to trace this upward movement, a filament was fixed to a sub-peduncle bearing a capsule nearly ripe, which was beginning to bend upwards by the two means just described. Its zourse was traced (see C, Fig. 188) during 53 h., by which time it had become nearly upright. The course is seen to be strongly zigzag, together with some little loops. We may therefore con- clude thai the movement consists of modified circumnutation.

The several species of Oxalis probably profit in the following manner by their sub-peduncles first bending downwards and then upwards. They are known to scatter their seeds by the burs'ing of the capsule; the walls of which are so extremely thin, like silver paper, that they would easily be permeated by rain. But as soon as the petals wither, the sepals rise up and enclose the young capsule, forming a perfect roof over it as soon as the sub-peduncle has bent itself downwards. By its subsequent upward movement, the capsule stands when ripe at a greater height above the ground by twice the length of the sub-peduncle, than it did when dependent, and is thus able to scatter its seeds to a greater distance. The sepals, which enclose the ovarium whilst it is young, present an additional adaptation by expanding widely when the seeds are ripe, so as not to interfere with their dispersal. In the case of Ozalis aretosella, the capsules are said sometimes to bury themselves under loose leaves or moss on the ground, but this cannot occur ° with those of O. carnosa, as the woody stem is too high.

Ovalis ucetosella.—The peduncles are furnished with a joint in Oaalis ih oe pursued by the upper part of a peduncle, whilst mising, traced from 11 a.m. June Ist to9 a.m. 3rd. Fiour duced to one-half of the original scale. pure ere (re the middle, so that the lower part auswers to the main peduncle and the upper part to one of the sub-peduncles of 0. ca? nosa, The upper part bends downwards, after the flower has begun to wither, and the whole peduncle then forms a hook; that this bending is due to epinasty we may infer from the case of O. carnosa, When the pod is nearly ripe, the upper part straightens itself and becomes erect ; and this is due to hypo- nasty or apogeotropism, or both combiued, and not to helio- tropism, for it occurred in darkness. The short, hooked part of the peduncle of a cleistogamic flower, bearing a pod nearly ripe, was observed in the dark during three days. The apex of the pod at first pointed perpendicularly down, but in the course of three days rose 90°, so that it now projected horizontally. The course during the two latter days is shown in Fig. 189; and it may be seen how greatly the peduncle, whilst rising, cireum- nutated. The lines of chief movement were at right angles to the plane of the originally hooked part. The tracing was not continued any longer; but after two additional days, tho peduncle with its capsule had become straight and stood upright.

Concluding Remarks on Apogeotropism.—When apo- geotropism is rendered by any means feeble, it acts, as shown in the several foregoing cases, by increasing the always present circumnutating movement in a direction opposed to gravity, and by diminishing that in the direction of gravity, as well as that to either side. The upward movement thus becomes unequal in rate, and is sometimes interrupted by stationary periods. Whenever irregular ellipses or loops are still formed, their longer axes are almost always directed in the line of gravity, in an analogous manner as occurred with heliotropic movements in reference to the light. As apogeotropism acts more and more energetically, ellipses or loops cease to be formed, and the course becomes at first strongly, and then less and less zigzag, and finally rectilinear. From thir grada- tion in the nature of the movement, and more especially from all growing parts, which alone (except when pul- vini are present) are acted on by apogeotropism, con-

tinually circLmnutating, we may conclude that even a rectilinear course is merely an extremely modified form of circumnutation. It is remarkable that a stem or other organ which is highly sensitive to apogeo- tropism, and which has bowed itself rapidly upwards in a straight line, is often carried beyond the vertical, as if by momentum. It then bends a little backwards to a point round which it finally cireumnutates. Two instances of this were observed with the hypocotyls of Beta vulgaris, one of which is shown in Fig. 188, and two other instances with the hypocotyls of Brassica. This momentum-like movement probably results from the accumulated effects of apogeotropism. For the sake of observing how long such after-effects lasted, a pot with seedlings of Beta was laid on its side in the dark, and the hypocotyls in 3h. 15m. became highly inclined. The pot, still in the dark, was then placed upright, and the movements of the two hypocotyls were traced; one continued to bend in its former direction, now in opposition to apogeotropism, for about 37 m., perhaps for 48 m.; but after 61 m. it moved in an opposite direction. ‘The other hypocotyl continued to move in its former course, after being placed upright, for at least 37 m.

Different species and different parts of the same species are acted on by apogeotropism in very dif- ferent degrees. Young seedlings, most of which cir- cumnutate quickly and largely, bend upwards and become vertical in much less time than do any older plants observed by us; but whether this is due to their greater sensitiveness to apogeotropism, or merely to their greater flexibility we do not know. A hypo- cotyl of Beta traversed an angle of 109° in 3h. 8 m., and a cotyledon of Phalaris an angle of 130° in 4 h. 30m. On the other hand, the stem of a herbaceous

Verbena rose 90° in about 24 h.; that of Rubus 67°, in 70h.; that of Cytisus 70°, in 72h.; that of a young American Oak only 37°, in 72h. The stem of a young Cyperus alternifolius rose only 11° in 96 h.; the bending being confined to near its base. Though the sheath-like cotyledons of Phalaris are so extremely sensitive to apogeotropism, the first true leaves which protrude from them exhibited only a trace of this action. Two fronds of a fern, Nephrodiwm molle, both of them young and one with the tip still inwardly curled, were kept in a horizontal position for 46 h., and during this time they rose so little that it was doubtful whether there was any true apogeotropic movement.

The most curious case known to us of a difference in sensitiveness to gravitation, and consequently of movement, in different parts of the same organ, is that offered by the petioles of the cotyledons of Ipomea lertophylla. The basal part for a short length where united to the undeveloped hypocotyl and radicle is strongly geotropic, whilst the whole upper part is strongly apogeotropic. But a portion near the blades of the cotyledons is after a time acted on by epinasty and curves downwards, for the sake of emerging in the form of an arch from the ground; it subsequently straightens itself, and is then again acted on by apo- geotropism.

A branch of Cucurbita ovifera, placed horizontally, moved upwards during 7 h. in a straight line, until it stood at 40° above the horizon; it then began to cir- cumnutate, as if owing to its trailing nature it had no tendency to rise any higher. Another upright branch was secured to a stick, close to the base of a tendril, and the pot was then laid horizontally in the Cark. In this position the tendril circumnutated and made several large ellipses during 14 h., as it likewise did on the following day; but during this whole time it was not in the least affected by apogeotropism. On the other hand, when branches of another Cucurbitaceous plant, Echinocytis lobata, were fixed in the dark so that the tendrils depended beneath the horizon, these began immediately to bend upwards, and whilst thus moving they ceased to circumnutate in any plain manner; but as soon ag they had become horizontal they re- commenced to revolve conspicuously.* The tendrils of Passiflora gracilis are likewise apogeotropic. Two branches were tied down so that their tendrils pointed many degrees beneath the horizon. One was observed for 8 h., during which time it rose, describing two circles, one above the other. The other tendril rose in a moderately straight line during the first 4 h., making however one small loop in its course; it then stood at about 45° above the horizon, where it cireum- nutated during the remaining 8 h. of observation.

A part or organ which whilst young is extremely sensitive to apogeotropism ceases to be so as it grows old; and it is remarkable; as showing the independence of this sensitiveness and of the circumnutating move- ment, that the latter sometimes continues for a time after all power of bending from the centre of the earth has been lost. Thus a seedling Orange bearing only 3 young leaves, with a rather stiff stem, did not curve in the least upwards during 24 h. whilst extended horizontally ; yet it circumnutated all the time over a small space. The hypocotyl of a young seedling of Cassia tora, similarly placed, became vertical in 12h.; that of an older seedling, 1} inch in height,

* For details see ‘The Movements and Habits of Climbi ise ie, abits of Climbing Plants, became so in 28h.; and that of another still older one, 14 inch in height, remained horizontal during two days, but distinctly circumnutated during this whole time. When the cotyledons of Phalaris or Avena are laid horizontally, the uppermost part first bends upwards, and then the lower part; consequently, after the lower part has become much curved upwards, the upper part ‘is compelled to curve backwards in an opposite direc- tion, in order to straighten itself and to stand ver- tically ; and this subsequent straightening process is likewise due to apogeotropism. The upper part of 8 young cotyledons of Phalaris were made rigid by being cemented to thin glass rods, so that this part could not bend in the least; nevertheless, the basal part was not prevented from curving upward. A stem or other organ which bends upwards through apogeo- tropism exerts considerable force; its own weight, which has of course to be lifted, was sufficient in almost every instance to cause the part at first to bend a little downwards; but the downward course was often rendered oblique by the simultaneous circum- nutating movement. The cotyledons of Avena placed horizontally, besides lifting their own weight, were able to furrow the soft sand above them, so as to leave little crescentic open spaces on the lower sides of their bases; and this is a remarkable proof of the force exerted.

As the tips of the cotyledons of Phalaris and Avena bend upwards through the action of apogeotropism before the basal part, and as these same tips when excited by a lateral light transmit some influence to the lower part, causing it to bend, we thought that the same rule might hold good with apogeotropism. Consequently, the tips of 7 cotyledons of Phalaris were cut off for a length in three cases of ‘2 inch and in the four other cases of '14, 12, °1, and -07 inch. But these cotyledons, after being extended horizontally, bowed themselves upwards as effectually as the un-. mutilated specimens in the same pots, showing that sensitiveness to gravitation is not confined to their tips.

This movement is directly the reverse of apogeo- tropism. Many organs bend downwards through epi- nasty or apheliotropism or from their own weight ; but we have met with very few cases of a downward move- ment in sub-aérial organs due to geotropism. We shall, however, give one good instance in the following section, in the case of Trifolium subterraneum, and . probably in that of Arachis hypogea. On the other hand, all roots which penetrate the ground (including the modified root-like petioles of Megarrhiza and Ipomea leptophylla) are guided in their downward course by geotropism; and so are many aérial roots, whilst others, as those of the Ivy, appear to be indifferent to its action. In our first chapter the movements of the radicles of several seedlings were described. We may there see (Fig. 1) how a radicle of the cabbage, when pointing vertically upwards so as to be very little acted on by geotropism, circum- nutated ; and how another (Fig. 2) which was at first placed in an inclined position bowed itself downwards in a zigzag line, sometimes remaining stationary for a time. Two other radicles of the cabbage travelled downwards in almost rectilinear courses. A radicle of the bean placed upright (Fig. 20) made a great sweep and zigzagged; but as it sank downwards and was more strongly acted on by geotropism, it moved in an

almost straight course. A radicle of Cucurbita, directed upwards (Fig. 26), also zigzagged at first, and de- scribed small loops; it then moved in a straight line. Nearly the same result was observed with the radicles of Zea mays. But the best evidence of the intimate connection between circumnutation and geotropism was afforded by the radicles of Phaseolus, Vicia, and Quercus, and in a less degree by those of Zea and fEsculus (see Figs. 18, 19, 21, 41, and 52); for when these were compelled to grow and slide down highly inclined surfaces of smoked glass, they left distinctly serpentine tracks.

The Burying of Seed-capsules: Trifolium subterranewum—The flower-heads of this plant are remarkable from producing only 3 or 4 perfect flowers, which are situated exteriorly. All the other many flowers abort, and are modified into rigid points, with a bundle of vessels running up their centres. After a time 5 long, elastic, claw-like projections, which represent the divi- sions of the calyx, are developed un their summits. As soon as the perfect flowers wither they bend downwards, supposing the peduncle to stand upright, and they then closely surround its upper part. This movement is due to epinasty, as is likewise the case with the flowers of 7. repens. The imperfect central flowers ultimately follow, one after the other, the same course. Whilst the perfect flowers are thus bending down, the whole peduncle curves downwards and increases much in length, until the flower-nead reaches the ground. Vaucher* says that when the plant is so placed that the heads cannot soon reach the ground, the peduncles grow to the extraordinary length of, from 6 to 9 inches. In whatever position the branches may be placed, the upper part of the peduncle at first bends vertically upwards through heliotropism; but as soon as the flowers begin to wither the downward curvature of the whole peduncle commences. As this latter movement occurred in complete darkness, and with peduncles arising from upright and from dependent branches, it cannot be due to apheliotropism or to epinasty, but must be attributed to geotropism. Ninc teen

upright flower-heads, arising from branches in all sorts of oe tions, on plants growing in a warm greenhouse, were marke with thread, and after 24h. six of them were vertically depen- dent; these therefore had travelled through 180° in this time. Ten were extended sub-horizontally, and these had moved through about 90°. Three very young peduncles had as yet moved only a little downwards, but after an additional 24h, were greatly inclined. At the time when the flower-heads reach the ground, the younger imperfect flowers in the centre are still pressed closely together, and form a conical projection; whereas the perfect and imperfect flowers on the outside are upturned and closely sur- round the peduncle. They are thus adapted to offer as little resistance, as the case admits of, in penetrating the ground, though the diameter of the flower-head is still considerable. The means by which this penetration is effected will presently be described. The flower-heads are able to bury themselves in common garden mould, and easily in saud or in fine sifted cinders packed rather closely. The depth to which they pene- trated, measured from the surface to the base of the head, was between + and 3 inch, but in one case rather above 0°6 inch, With a plant kept in the house, a head partly buried itself in sand in 6h.: after 3 days only the tips of the reflexed calyces were visible, and after 6 days the whole had disappeared. But with plants growing out of doors we believe, from casual obser- vations, that they bury themselves in a much shorter time.

After the heads have buried themselves, the central aborted flowers increase considerably in length and rigidity, and become bleached. They gradually curve, one after the other, upwards or towards the peduncle, in the same manner as did the perfect flowers at first. In thus moving, the long claws on their summits carry with them some earth. Hence a flower- head which has been buried for a sufficient time, forms a rather large ball, consisting of the aborted flowers, separated from one another by earth, and surrounding the little pods (the product of the perfect flowers) which lie close round the upper part of the peduncle. The calyces of the perfect and imperfect flowers are clothed with simple and multicellular hairs, which have the power of absorption i for when placed in a weak solution of carbonate of ammonia 7 gr. to 1 oz. of water) their proto- plasmic contents immediately became aggregated and afterwarda displayed the usual slow movements. This clover generally

grows in dry soil, but whether the power of absorption by the hairs on the buried flower-heads is of any importance to them we do not know. Only a few of the flower-heads, which from their position are not able to reach the ground and bury them- selves, yield seeds; whereas the buried ones never failed, as far as we observed, to produce as many seeds as there had been perfect flowers. Trifolium subterraneum : downward movement of peduncle from 19° beneath the horizon to a nearly vertically dependent position, traced from 11 a.m. July 22nd to the morning of 25th. Glass filament fixed transversely across peduncle, at base of flower-head.

curving down to the ground. We have seen in Chap. IV., Fig. 92, p. 225, that an upright young flower-head circumnu- tated conspicuously; and that this movement continued after the peduncle had begun to bend downwards. The same peduncle was observed when inclined at an angle of 19° abc ra the horizon, and it circumnutated during two days. Another which was already curved 36° beneath the horizon, was observed from 11 a.m. July 22nd to the 27th, by which latter date it had become vertically dependent. Its course during the first 12 h. is shown in Fig. 190, and its position on the three succeeding mornings until the 25th, Fig. 191, when it was nearly vertical. During the first day the peduncle clearly circumnutated, for it moved 4 times down and 3 times up; and on each succeeding day, as it sank downwards, the same movement continued, but was only occasionally observed and was less strongly marked. It should Trifolium subterraneum : cir- be stated that these peduncles were cumoutating movement of observed under a double skylight in peduncle, whilst the flower- the house, and that they generally head was burying itself in toyed downwards very much more sand, with the reflexed tips ‘ of the calyx still visible; Slowly than those on plants growing traced from 8 a.m. July out of doors or in the greenhouse. 26th to 9 AM. on 27th. ‘The movement of another vertically Glass filament fixed trans- denendent. ped les wikke tea. a : versely across peduncle, G@Pendent peduncle wi € lower: near flower-head. head standing half an inch above the ground, was traced, and again when it first touched the ground; in both cases irregular ellipses were described every 4 or 5h. A peduncle on a plant which had been brought into the house, Fig. 192. moved from an upright into a ver- tically dependent position in a single day; and here the course during the first 12 h. was nearly straight, but with a few well-mark:d Trifolium subterraneum ; move- zigzags which betrayed the essential ment of same peduncle, with nature of the movement. Lastly, flower-head completely buried the circumnutation of a peduncle beneath the sand; traced from i ‘ 8 a.a.to7.15¥.M. on July 29th, WS traced during 51h.

whilst in the act of burying itself obliquely in a little heap of sand. After it had buried itself to such a depth that the tips of the sepals were alone visible, the above figure (Fig. 191) was traced during 25 h. When the flower- head had completely disappeared beneath the sand, another tracing was made during 11h. 45 m. (Fig. 192); and here again we see that the peduncle was circumnutating. Any oue who will observe a flower-head burying itself, will be convinced that the rocking n ovement, due to the continued circumnutation of he peduncle, plays an important part in the act. Considering that the flower-heads are very light, that the peduncles are long, thin, and flexible, and that they arise from flexible branches, it is incredible that an object as blunt as one of these flower-heads could penetrate the ground by means of the growing force of the peduncle, unless it were aided by the vocking movement. After a flower-head has penetrated the ground to a small depth, another and efficient ager.cy comes into play; the central rigid aborted flowers, each terminating in five long claws, curve up towards the peduncle; and in doing so can hardly fail to drag the head down to a greater depth, aided as this action is by the circumnutating movement, which con- tinues after the flower-head has completely buried itself. The aborted flowers thus act something like the hands of the mole, which force the earth backwards and the body forwards.

It is well known that the seed-capsules of various widely distinct plants either bury themselves in the ground, or are produced from imperfect flowers developed beneath the surface. Besides the present case, two other well-marked instances will be immediately given. It is probable that one chief good thus gained is the protection of the seeds from animals which prey on them. In the case of 7. subterranewm, the seeds are not only concealed by being buried, but are likewise protected by being closely surrounded by the rigid, aborted flowers. We may the more confidently infer that protection is here aimed at, because the seeds of several species in this same genus are protected in other ways ;* namely, by the swelling and closure of the calyx, or by the persistence and bending down of the standard-petal, é&c. But the most curious instance is that of 7. globosum, in which the upper flowers are stcrile, as in 7° sublerraneum, but are here developed into large brushes of hairs which envelop and protect the seed-bearing flowers. Nevertheless, in all these cases the capsules, with their seeds, may profit, as Mr. T. Thiselton Dyer has remarked,t by their being kept somewhat damy and the advantage of such dampness perhaps throws light on the pre- sence of the absorbent hairs on the buried flower-heads of 7. sud- terraneum. According to Mr. Bentham, as quoted by Mr. Dyer,

the prostrate habit of Helianthemum prostratum “brings the capsules in contact with the surface of the ground, postpones their maturity, and so favours the seeds attaining a larger size.” The capsules of Cyclamen and of Omulis ucetosclla are only occa- sionally buried, and this only beneath dead leaves or moss. If it be an advantage to a plant that its capsules should be kept damp and cool by being laid on the ground, we have in these latter cases the first step, from which the power of penetrating the ground, with the aid of the always present movement of circumnutation, might afterwards have been gained.

Arachis hyp gea—The flowers which bury themselves, rise from stiff branches a few inches above the ground, and stand upright. After they have fallen off, the gynophore, that is the part which supports the ovarium, grows to a great length, even to 8 or 4 inches, and bends perpendicularly downwards. It resembles closely a peduncle, but has a smooth and pointed apex, which contains the ovules, and is at first not in the least enlarged. The apex after reaching the ground penetrates it, in one case observed by us to a depth of 1 inch, and in another to 0:7 inch. It there becomes developed into a large pod. Flowers which are seated too high on the plant for the gyno- phore to reach the ground are said* never to produce pods,

The movement of a young gynophore, rather under an inch in length and vertically dependent, was traced during 46 h. by means of a glass filament (with sights) fixed transversely a little above the apex. It plainly circumnutated (Fig. 198) whilst increasing in length and growing downwards. It was then raised up, 80 as to be extended almost horizontally, and the terminal part curved itself downwards, fo'lowing a nearly straight course during 12h., but with one attempt to circum- nutate, as shown in Fig. 194. After 24 h. it had become nearly vertical. Whether the exciting cause of the. downward move- ment is geotropism or apheliotropism was not ascertained; but probably it is not apheliotropism, as all the gynophores grew straight down towards the ground, whilst the light in the hot- house entered from one side as well as from above. Another and older gynophore, the apex of which had nearly reached the ground, was observed during 3 days in the same manner as the first-mentioned short one; and it was found to be always circum- nutating. During the first 84 h. it described a figure which

represented four ellipses. Lastly, a long gynophore, the apex of which had buried itself to the depth of about half an inch, was Arachis hypogex: circum- Arachis hypoy@a: down nutation of vertically ward movement of same dependent young gyno- young gynophore, after phore, traced on a ver- being extended horizon- tical glass from 10 A.M. tally; traced on a vertical July 31st to 8 a.m. Aug. glass from 8.30 a.M. to 2nd. 8.30 p.m. Aug. 2nd. pulled up and extended horizontally: it quickly began to curve downwards in a zigzag line; but on the following day the ter-

minal bleached portion was a little shrivelled. As the gyno- phoves are rigid and arise from stiff branches, and as they terminate in sharp smooth points, it is probable that they could penetrate the ground by the mere force of growth. But this action must be aided by the circumnutating movement, for fine sand, kept moist, was pressed close round the apex of a gyno- phore which had reached the ground, and after a few hours it was surrounded by a narrow open crack. After three weeks this gynophore was uncovered, and the apex was found at a depth of rather above half an inch developed into a small, white, oval pod.